The invention relates to the field of machinery venting. More specifically, the invention provides a novel vent for an enclosure containing lubricated machinery.
Gas-permeable, liquid-impermeable vents find use in many applications in the automotive industry, such as electrical component housings, gear housings, vehicle bodies, brake housings, etc. where pressure equalization between the housing interior and surrounding environment must occur. While vents must allow for gas pressure equalization, they must also seal the interior of the housing from liquid, dirt and dust particles. Failure to exclude liquids such as water can damage the components and corrode the housing.
Machinery enclosures such as gearbox housings, axles and the like are subject to thermal cycling. As the machinery is operated, temperatures of the lubricant and internal air begin to rise, causing air pressure to rise in the enclosure. When the machinery is stopped, pressure falls within the enclosure. To accommodate changes in air pressure from operating temperature changes, vents are required. If effective venting is not provided, seals and gaskets may be compromised. It is important that contaminants be prevented from entering the machinery enclosure. Contaminants and water will severely degrade the effectiveness of lubricant, which results in premature wear of the machinery.
Machinery vents have incorporated expanded Polytetrafluoroethylene (ePTFE) membranes. Such membranes are known for water impermeabily and air permeability and therefore not only prevent contaminants from entering the gear case, but also contain the lubricant to prevent spillage. However, ePTFE vents are subject to rapid blinding as lubricant aerosol particles fill the membrane pores and block airflow. Accordingly, known ePTFE vents had limited service life.
Other attempts at venting machinery spaces have incorporated baffles, coalescing media or valve assemblies which permit expanding air to escape through valve openings. During cooling periods, such assemblies permit air ingress through a second valve assembly, or through a membrane. Such assemblies necessarily incorporate numerous moving parts which are subject to wear and have increased assembly complexity.
Some machinery vents are mounted remotely from the machinery. Remote mounting allows the vent to be placed in an area with limited environmental exposure, and could reduce the problems associated with lubricant blinding. Other gear cases incorporate a simple snorkel to vent the case to a remote and relatively protected area. Such snorkels provide little protection from contamination and will not prevent lubricant spillage. Moreover, all remote mounting approaches introduce additional parts cost and installation complexity.
What is needed is a vent without moving parts that can be mounted in close proximity or directly to a machinery enclosure that allows adequate air passage, prevents contaminants and liquid from entering the machinery space, and retains liquids inside the enclosure in the event it is oriented to allow liquids to contact the vent.